Tissular expression and regulation of type 1 angiotensin II receptor subtypes by quantitative reverse transcriptase-polymerase chain reaction analysis

Recent studies have revealed that angiotensin II (Ang II) interacts with two pharmacologically different types of seven-transmembrane domain receptors, hence named Ang II type 1 and type 2 (AT1 and AT2) receptors. cDNAs for the AT1 receptor have been cloned, and the existence of two receptor subtypes, AT1A and AT1B, has been revealed in rat and mouse. This study presents a new approach for the specific quantification of AT1A and AT1B receptor mRNAs by reverse transcription and polymerase chain reaction amplification in the presence of an AT1 receptor mutant cRNA as internal standard. Absolute quantities of mRNA are then determined by extrapolation using the standard curve generated with the internal standard. Moreover, addition of this internal standard to each tube controls for both reverse transcription and polymerase chain reaction amplification in each sample. In male Wistar rats, the highest absolute AT1A receptor mRNA levels were found in liver and kidney and those for AT1B receptor mRNA in the pituitary. Expressed as a percentage of total AT1A+AT1B receptor mRNA content, AT1A receptor mRNA content was 100% in liver, 85% in lung, 73% in kidney, 65% in aorta, 48% in adrenals, and 15% in the hypophysis. Since this approach can determine absolute AT1A and AT1B receptor mRNA quantities in different organs, it allows the study of the regulation of their expression under different pathophysiological conditions. After sodium depletion, known to induce hyperactivity of the renin-angiotensin system, adrenal AT1A and AT1B receptor mRNA levels were increased by 60% and 110%, respectively. In contrast, in renovascular hypertension (two-kidney, one clip), also associated with elevated circulating plasma renin activity, adrenal AT1B receptor mRNA levels decreased by 50%, whereas there was no change in those of AT1A. Therefore, the differential distribution and regulation of these two receptor subtypes suggest that each of them might be involved in the mediation of different biological effects of Ang II.

Use of a monoclonal antibody to detect DNA damage caused by the anticancer drug cis-diamminedichloroplatinum (II) in vivo and in vitro

A monoclonal antibody, MAb62-5, was prepared and used to detect DNA damage due to the anticancer drug cis-diamminedichloroplatinum (II) (or cisplatin). ELISA competition indicated that the binding of MAb62-5 to cisplatin-DNA was competitively inhibited (50% control) by 210 nM of cisplatin bound to DNA, cisplatin/nucleotide (D/N) = 0.2. Using a DNA mobility shift assay, MAb62-5 binding activity was inhibited by 50% by approximately 50-fold molar excess of cisplatin-DNA adducts (D/N = 0.08), whereas there was less than 5% inhibition by UV-DNA adducts or mock-treated DNA. In addition, MAb62-5 showed a similar affinity to the cisplatin-DNA adducts as compared to an endogenous cisplatin-damaged DNA recognition protein. Using ELISA with this antibody, we have demonstrated a 2-fold enhancement in excision repair of cisplatin-DNA adducts in resistant HeLa cells. This is supported by the measurement of repair-associated DNA strand breaks using alkaline elution and host cell reactivation of transfected plasmid DNA carrying cisplatin damage. These findings also provide explanation for the complexicity of immunoassay in cells.

[Fine needle aspiration cytology and influencing factors in breast cancer]

The results of 200 women with primary breast cancer who had fine needle aspiration cytology prior to definitive surgery at the Peking Union Medical College Hospital were presented. Among them, aspiration cytology was positive and suspicious in 87% (174/200) and pseudonegative in 13% (26/200). Clinical factors relating to the success of these aspiration were evaluated. The most significant factor was which physician performed the aspiration. Size of the lesion and type of the cancer were also important influences on the aspiration. Experiences in aspiration cytology were introduced by author.

Alterations in angiotensin II receptor mediated signal transduction shortly after coronary artery constriction in the rat

OBJECTIVE

The aim of the study was to determine the effect of coronary artery constriction on the density of angiotensin II receptors and on the effector responses coupled with these receptors on myocytes one week after surgical induction of coronary artery stenosis in rats.

METHODS

After induction of coronary artery stenosis and following the estimation of global cardiac performance, myocytes were enzymatically dissociated and radioligand binding studies were performed. In addition, the isotonic contractile performance, cytosolic calcium transients, and angiotensin II stimulated inositol phosphate generation in myocytes were measured in the presence and absence of the angiotensin II receptor subtype antagonist losartan.

RESULTS

After documenting left ventricular failure and right ventricular dysfunction, the expression and density of angiotensin II receptors in left ventricular myocytes were evaluated and found to be increased 3.1-fold and 4.1-fold, respectively. Corresponding increases in right ventricular myocytes were 3.6-fold and 4.5-fold. In contrast, the quantity of the regulatory protein Gq alpha was not altered in either ventricle. Angiotensin II did not increase the generation of total inositol phosphates in left and right ventricular myocytes at maximum stimulation. However, the threshold for the formation of inositol phosphates was lowered in left ventricular myocytes of coronary narrowed rats. Measurements of single cell mechanics indicated that angiotensin II stimulation markedly improved the depression in myocyte function biventricularly. This inotropic effect was coupled with the restoration of cytosolic calcium.

CONCLUSIONS

The upregulation of angiotensin II receptors on myocytes in this model of global ischaemia may be a compensatory mechanism ameliorating myocyte contractility in an attempt to sustain ventricular pump function.

Modified signed-digit arithmetic based on redundant bit representation

Fully parallel modified signed-digit arithmetic operations are realized based on redundant bit representation of the digits proposed. A new truth-table minimizing technique is presented based on redundant-bitrepresentation coding. It is shown that only 34 minterms are enough for implementing one-step modified signed-digit addition and subtraction with this new representation. Two optical implementation schemes, correlation and matrix multiplication, are described. Experimental demonstrations of the correlation architecture are presented. Both architectures use fixed minterm masks for arbitrary-length operands, taking full advantage of the parallelism of the modified signed-digit number system and optics.

Discrepancy between plasma and lung angiotensin-converting enzyme activity in experimental congestive heart failure. A novel aspect of endothelium dysfunction

The renin-angiotensin and cardiac natriuretic systems play an important role in the pathophysiology of congestive heart failure (CHF). The status of the membrane-bound pulmonary and renal activities of three ectoenzymes involved in the regulation of these systems-angiotensin-converting enzyme (ACE), neutral endopeptidase (NEP), and aminopeptidase A (APA)-was investigated in Wistar rats 3 months after induction of myocardial infarction (MI) and in sham-operated (control) rats. Plasma renin activity and ACE activity, plasma angiotensin II (Ang II) levels, and atrial natriuretic factor levels were simultaneously determined. The lung ACE activity was decreased in MI rats compared with control rats (P < .0001), and this decrease depended on the severity of the heart failure. In contrast, plasma ACE activity was increased in MI rats (P < .01), and this increase was also proportional to the severity of MI. Northern blot analysis showed that the lung ACE mRNA level in severe MI rats was half that of the control rats. Renal ACE activity of the MI rats was not affected, and neither renal or pulmonary NEP nor pulmonary APA activities were altered. Thus, lung ACE gene expression appears to be both organ- and enzyme-specifically regulated during CHF. Whereas plasma renin was increased in heart failure rats, plasma Ang II levels were not different from those of control rats. Thus, decreased lung ACE activity could possibly contribute to keeping plasma Ang II levels in the normal range. The decrease in lung ACE activity and mRNA levels, combined with increased plasma ACE activity, represents a novel aspect of endothelial dysfunction in CHF.(ABSTRACT TRUNCATED AT 250 WORDS)

[Study on auto-solidified tumor vaccine]

In order to evaluate the immune effect of Auto-solidified tumor vaccine induced by thermal doses of 65 degrees C for 5 minutes on the killing and inactivation of cancer cells in operation, a series of experimental and clinical studies were carried out, the results showed that Balb/c mice immunized with ASTV could tolerate the aggression of H22 3 x 10(8) cancer cells with efficiency of 93.3% (28/30), the inoperable advanced hepatic cancer proved in operation was hypothermited and ASTV was made for immune injection postoperatively, with the clinical efficiency 76.8% (53/69), and 5-year survival rate 23% (9/39), the difference with control group is significant. In recent years, it is recognized once again that tumor can induce specific immunity. The most important matter is how to stimulate the host to produce effective cellular immunity. Our results showed that the thermal biological effect could inactivate cancer cell and change nuclear antigen in host net-like immunity system. Under gene regulation, the host can obtain the cellular immune effect against cancer cells.

Allozyme diversity in Chinese, Seguin and American chestnut (Castanea spp.)

Allozyme genetic variability in three chestnut (Castanea) species was investigated using 19 loci from ten enzyme systems. G-tests of heterogeneity of isozymic allele distribution showed significant differences between the three species at 15 of the 19 loci, and between the 13 C. mollissima populations at 13 of the 19 loci examined. C. mollissima was found to possess a significantly-higher value of mean gene heterozygosity (H=0.3050±0.0419), the percentage of polymorphic loci (P=84.21%) and the average number of alleles per locus (A=2.05), than any other species in the Castanea section Eucastanon. When the genetic variability of populations of C. mollissima from four regions in China was investigated, the population from the Changjiang river region showed a markedly higher mean gene heterozygosity (H=0.3480±0.0436) than populations from the other regions. Genetic relationships among the four regions were assessed by Nei's genetic identity I and standard genetic distance D. An approximately-identical distance between the population from the Changjiang river region and populations from the three other regions was observed, while populations from the latter regions showed almost the same genetic distance from each other. These data, when considered with information existing prior to this study, contribute to an understanding of the possible origin and progenitor of the chestnut species.

Relation between age, arterial distensibility, and aortic dilatation in the Marfan syndrome

This study examined the relations between age, arterial distensibility, and systemic hemodynamics in patients with the Marfan syndrome. The study group included 170 patients referred to a specialist clinic, of whom 55 (age 26 +/- 12 years) were diagnosed as having Marfan syndrome. The remaining 115 patients (age 25 +/- 14 years) formed a control group. Each patient underwent echocardiographic examination, with measurement of ascending aorta diameter at end-diastole and end-systole, and aortic flow velocities. The elastic properties of the aorta were indexed by calculation of aortic distensibility, wall stiffness, and systemic pulse wave velocity. Mean end-diastolic aortic diameter in the Marfan group (38 +/- 9 mm) was greater than that in the controls (26 +/- 4 mm, p < 0.01). Resting heart rate and aortic flow velocities were similar in the 2 groups, but systemic arterial pulse pressure was greater in the Marfan group (50 +/- 12 mm Hg) than in the controls (41 +/- 8 mm Hg, p < 0.01). Aortic diameter increased with age in both groups, but at all ages the Marfan group exhibited greater aortic diameters (p < 0.05). Aortic distensibility was less in the Marfan group (2.6 +/- 1.3 cm2.dynes-1 x10(-6)) than in the controls (6.2 +/- 2.1 cm2.dynes-1 x 10(-6), p < 0.01), and the aortic wall stiffness index was greater in the Marfan group (7.9 +/- 3.4) than in the controls (2.8 +/- 0.6, p < 0.01). Aortic wall stiffness increased with age and aortic diameter, but at all ages the Marfan group exhibited a stiffer aorta for a given diameter than did the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of brain injury with deep hypothermic circulatory arrest and protective effects of coenzyme Q10

Sixteen dogs, divided randomly into a control group and coenzyme Q10 group (10mg/kg, intraperitoneally before the operation), underwent deep hypothermic circulatory arrest with cardiopulmonary bypass, as is done clinically. At four time points cerebral cortex and cerebrospinal fluid specimens were collected to study free radical formation, energy metabolism, and ultrastructure. During cardiopulmonary bypass cerebral electron spin resonance spectra and malondialdehyde contents were progressively higher than before bypass, especially at the 60 minutes of circulatory arrest and 30 minutes of reperfusion (p1 < 0.01, p2 < 0.05). In the coenzyme Q10 group at the latter two time points, they had increased less than in the control group at same time points (p1 < 0.02, p2 < 0.005). Adenosine triphosphate content in the cortex during bypass decreased gradually from the prebypass level (p1 < 0.02, p2 = p3 < 0.001), while lactate in cerebrospinal fluid increased (p1 < 0.05, p2 = p3 < 0.001). In the coenzyme Q10 group, adenosine triphosphate at the latter two time points was greater than that in the control group (p1 = p2 < 0.05), while the lactate changes were not significantly different from control at each time point (all p > 0.05). Ultrastructure of the cortex was normal before bypass and almost normal during bypass, but it was obviously abnormal at 60 minutes of circulatory arrest and more seriously abnormal at 30 minutes of reperfusion. In the coenzyme Q10 group the abnormality was obviously reduced. The results suggest that oxygen-derived free radicals and abnormal energy metabolism might play critical roles in brain ischemia/reperfusion injury. Coenzyme Q10 could protect the brain by improving cerebral metabolism.

Comparative RFLP mapping of an allotetraploid wild rice species (Oryza latifolia) and cultivated rice (O. sativa)

The purpose of this study was to construct a comparative RFLP map of an allotetraploid wild rice species, Oryza latifolia, and to study the relationship between the CCDD genome of O. latifolia and the AA genome of O. sativa. A set of RFLP markers, which had been previously mapped to the AA genome of cultivated rice, were used to construct the comparative map. Fifty-eight F2 progeny, which were derived from a single F1 plant, were used for segregation analysis. The comparative RFLP map contains 149 DNA markers, including 145 genomic DNA markers from cultivated rice, 3 cDNA markers from oat, and one known gene (waxy, from maize). Segregation patterns reflected the allotetraploid ancestry of O. latifolia, and the CC and DD genomes were readily distinguished by most probes tested. There is a high degree of conservation between the CCDD genome of O. latifolia and the AA genome of O. sativa based on our data, but some inversions and translocations were noted.

[Determination of E. coli with MUG (Fluorocult)-lauryl sulfate broth for the testing of microbial contamination in drugs]

A test method for the determination of Escherichia coli in plant materials with the MUG (Fluorocult)-lauryl sulfate broth is described. It was found that more than 75% of the commonly used vegetable drugs exhibit fluorescence quench effects to different degrees when determining E. coli with the MUG-lauryl sulfate broth. Therefore a simple combination of two procedures was evaluated in order to avoid the matrix interferences: in a first step the drug sample was diluted eight times in a proportion of 1:10 with MUG-lauryl sulfate broth in eight separate tubes from 1 g down to 10(-7) g/tube (1st test series) and the resulting samples were incubated for 40 h at 36 degrees C. Subsequently, the tubes were tested for fluorescence. If the first tube of this series was found without fluorescence, in a second step a subsequent series of MUG-lauryl sulfate broth (2nd test series) was inoculated with 0.5 ml of the incubated culture from each of the first three tubes of series 1 and incubated again for 24 h at 36 degrees C. The results were evaluated from gas production, fluorescence as well as indole formation. Thus, the method allowed a simple and reproducible enumeration of E. coli for the test on microbial contamination in medicinal plant materials. The method was successfully applied to samples of 38 vegetable drugs for quantitative determination of E. coli (8 samples were found being contaminated with E. coli).

Evidence for guanosine triphosphate--binding proteins in Trypanosoma cruzi

The transformation of the parasite Trypanosoma cruzi from the blood-borne trypomastigote to the intracellular amastigote constitutes a key clinical feature in the pathophysiology of Chagas' disease. That this transition occurs without change in the integrity of the plasma membrane of the parasite suggests the presence of biochemical structures, i.e., signal transduction systems, that convey information regarding the external milieu of the host so as to facilitate this transformation. In higher eukaryotes, it has been found that a heterotrimeric GTP-binding protein (G-protein), composed of alpha beta gamma subunits, constitutes a critical component of this complex. Two closely related groups of G-proteins are substrates for cholera toxin (CT)- (Gs) and pertussis toxin (PT)- (Gi1-3 and Go) dependent ADP ribosylation. In concert, they link plasma membrane receptors to adenylate cyclase, resulting in the stimulation or inhibition, respectively, of cAMP generation. In this report, we demonstrate the presence of both groups of G-proteins. Cholera toxin-dependent ADP ribosylation of 42- and 45-kD proteins was demonstrable in amastigotes (AMAST), in the cytosol of epimastigotes (EPI), and weakly in trypomastigotes (TRYP), suggesting the presence of the stimulatory GTP-binding protein, Gs, in T. cruzi. Antisera generated against the alpha s subunit of the Gs heterotrimeric protein (anti-alpha s) bound to a 45-kD protein CT substrate in the rank order TRYP >> AMAST approximately EPI cytosol. Immunoprecipitation of CT-32P-ADP-ribosylated membranes with anti-alpha s resulted in 42- and 45-kD proteins. However, no Gs-mediated activation of adenylate cyclase was demonstrable in reconstitution studies using cyc- lymphoma cells, which lack a functional Gs but possess a beta-adrenergic receptor and adenylyl cyclase enzyme. Pertussis toxin-catalyzed ADP ribosylation was demonstrable in 39-40-kD particulate proteins of EPI, less strongly in AMAST, and least in TRYP, consistent with the presence of inhibitory (Gi) and Go GTP-binding proteins. In support of this observation, immunochemical analysis of the PT substrates identified the presence of alpha o and alpha i1-2-3 in EPI, AMAST and TRYP, although, with the exception of alpha i3, both toxin and associated immunochemical PT substrates are decreased in AMAST and TRYP relative to EPI. Although the functions of these putative G-proteins in T. cruzi are still unclear, their expression may be regulated by the state of parasite differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Active oxygen species are involved in the induction of micronuclei by arsenite in XRS-5 cells

The human carcinogen, arsenic, is genotoxic to mammalian cells in vitro. The mechanism is largely unknown, although the involvement of free radicals has been suggested. Since the X-ray sensitive Chinese hamster ovary cell line, XRS-5, is also sensitive to several free-radical generating agents, including H2O2, we have used this cell line to test whether the genotoxic effect of arsenite is mediated via the generation of active-oxygen species. The results indicate that the XRS-5 cells are more sensitive to arsenite in terms of cell-killing and micronucleus induction compared to the parental CHO-K1 cells. The level of arsenic uptake and release, the levels of elementary components for arsenic detoxification, glutathione and glutathione S-transferase activities in these two cell lines are very similar. The XRS-5 cells, however, were shown to have 6-fold lower catalase activity in comparison to CHO-K1 cells. Moreover, catalase could effectively reduce the frequency of arsenite-induced micronuclei. These results indicate that the low catalase activity may be an important reason why XRS-5 cells are more sensitive to the toxic effects of arsenite, and arsenite probably induces micronuclei via the overproduction of H2O2. The XRS-5 cells had a higher background level of micronuclei, and were also more sensitive to gamma-rays in terms of induction of micronuclei. Catalase, however, did not reduce the background level or the frequency of gamma-ray-induced micronuclei. Therefore, the lower catalase activity seems to bear little relation to the high background level of micronuclei and the hypersensitivity to gamma-rays in micronucleus induction in XRS-5 cells.

Immune responses to Epstein-Barr virus in atomic bomb survivors: study of precursor frequency of cytotoxic lymphocytes and titer levels of anti-Epstein-Barr virus-related antibodies

Precursor frequencies of cytotoxic lymphocytes to autologous Epstein-Barr virus-transformed B cells and serum titers of anti-Epstein-Barr virus-related antibodies were measured in 68 atomic bomb survivors to clarify the immune mechanism controlling Epstein-Barr virus infection. The precursor frequency was negatively correlated with the titer of anti-early antigen IgG, which is probably produced at the stage of viral reactivation. A positive correlation between the precursor frequency and titer of anti-Epstein-Barr virus-associated nuclear antigen antibody was also observed, indicating that the precursor frequency reflects the degree of in vivo destruction by T cells of the virus-infected cells. These results suggest that T-cell memory specific to Epstein-Barr virus keeps the virus under control and that the precursor frequency assay is useful for the evaluation of immune responses to Epstein-Barr virus. However, no significant effect of atomic bomb radiation on the precursor frequency was observed in the present study, probably due to the limited number of participants.

Endogenous p53 protein generated from wild-type alternatively spliced p53 RNA in mouse epidermal cells

We previously demonstrated that a wild-type alternatively spliced p53 (p53as) RNA exists in mouse cultured cells and normal mouse tissues at approximately 25 to 33% of the level of the major p53 RNA form. The alternative RNA transcript is 96 nucleotides longer than the major transcript as a result of alternative splicing of intron 10 sequences. The protein expected to be generated from the p53as transcript is 9 amino acids shorter than the major p53 protein and has 17 different amino acids at the carboxyl terminus. We report here that p53as protein exists in nontransformed and malignant epidermal cells and is localized to the nucleus. In addition, p53as protein is preferentially expressed during the G2 phase of the cell cycle and in cells with greater than G2 DNA content compared with the major p53 protein, which is preferentially expressed in G1. The p53as immunoreactivity is elevated and shifted to the G1 phase of the cell cycle following actinomycin D treatment of nontransformed cells but not malignant cells. In view of the dimerization and tetramerization of p53 protein which may be necessary for its DNA binding and transcriptional activation activities, the presence of p53as protein in cells has important implications for understanding the physiological function(s) of the p53 gene.

Histocytochemistry of glycoconjugates in nasal inverted papilloma

In order to investigate the changes in cellular distribution of the glycocalyces in nasal inverted papilloma, formalin-fixed, paraffin-embedded biopsy specimens of inverted papilloma were analyzed by the avidin-biotin-peroxidase complex technique for the demonstration of peanut agglutinin (PNA) receptors, concanavalin A (Canavalia ensiformis agglutinin; ConA) receptors, carcinoembryonic antigen (CEA), and keratin, and compared with normal nasal mucosa, nasal polyps, and papillary adenocarcinoma. The inverted papillomas were positive for PNA and CEA, to the same degree as papillary adenocarcinoma. Their PNA binding was related to the degree of dysplasia. The ConA reaction was intermediate between that of normal mucosa and adenocarcinoma. The results suggest that the alteration of cellular glycoprotein structure in inverted papilloma is associated with its biologic characterization.

Derivatives of 3-alkyl-N-hydroxysuccinimide: probing the effect of structure on bioactivity toward human leukocyte elastase

A structure-activity relationship study was conducted in order to probe the nature of the interaction between some 3-alkyl-N-hydroxysuccinimide derivatives and human leukocyte elastase. The structural features in substituent X (structure I) that lead to the manifestation and optimization of inhibitory activity have been examined. The data suggest that the presence of an alkyl or aryl(sulfonyloxy) group in the active compounds may serve a triple purpose, namely, it functions as a good leaving group as dictated by the established mechanism of action of this class of compounds, secondly, it may enhance binding by assuming a favorable spatial orientation and, thirdly, it may increase the chemical reactivity of the carbonyl carbon in the bioactive compounds.

Thermal stabilities of hemoglobins crosslinked with different length reagents

Bis(3,5-dibromosalicyl) succinate and glutarate were used to crosslink met-, oxy- and deoxyhemoglobins. The added flexibility of these reagents compared to the fumarate analog resulted in a more heterogeneous product but did not greatly affect the maximum thermal stability of the crosslinked hemoglobins.

In vitro differentiation of B cells and myeloid cells from the early mouse embryo and its extraembryonic yolk sac

The yolk sac is the first site of hematopoiesis during ontogeny. However, the source of early embryonic hematopoietic stem cells remains unresolved. Early studies have shown that cells obtained from day-8 and -9 extraembryonic yolk sacs can give rise to T cells and myeloid cells, whereas the embryo itself appears to lack such cells. Controversy remains as to whether it is the embryo itself or the extraembryonic yolk sac that contains the initial precursors capable of differentiating into B cells. This study used the approach of enriching hematopoietic stem cells by immunocytoadherence and studying cells isolated from within the embryo itself or from the yolk sac obtained at days 8 and 9 of mouse embryonic development. We report that on day 9, both yolk sac-derived and embryo-derived cells can give rise to B cells and myeloid cells in vitro. On day 8, however, cells isolated from the yolk sac but not from the embryo produce myeloid colonies in vitro; neither source of stem cells generates B cells. Our study suggests that myeloid precursors migrate from yolk sac to embryo earlier than has previously been reported but that the origin for B cell precursors remains to be determined.

Genetic definition of the substrate selectivity of outer membrane porin protein OprD of Pseudomonas aeruginosa

Earlier studies proved that Pseudomonas aeruginosa OprD is a specific porin for basic amino acids and imipenem. It was also considered to function as a nonspecific porin that allowed the size-dependent uptake of monosaccharides and facilitation of the uptake of quinolone and other antibiotics. In the present study, we utilized P. aeruginosa strains with genetically defined levels of OprD to characterize the in vivo substrate selectivity of this porin. An oprD::omega interposon mutant was constructed by gene replacement utilizing an in vitro mutagenized cloned oprD gene. In addition, OprD was overexpressed from the lac promoter by cloning the oprD gene into the broad-host-range plasmid pUCP19. To test the substrate selectivity, strains were grown in minimal medium with limiting concentrations of the carbon sources glucose, gluconate, or pyruvate. In minimal medium with 0.5 mM gluconate, the growth rates of the parent strain H103 and its oprD::omega mutant H729 were only 60 and 20%, respectively, of that of the OprD-overexpressing strain H103(pXH2). In contrast, no significant differences were observed in the growth rates of these three strains on glucose or pyruvate, indicating that OprD selectively facilitated the transport of gluconate. To determine the role of OprD in antibiotic uptake, nine strains representing different levels of OprD and OprF were used to determine the MICs of different antibiotics. The results clearly demonstrated that OprD could be utilized by imipenem and meropenem but that, even when substantially overexpressed, it could not be significantly utilized by other beta-lactams, quinolones, or aminoglycosides. In addition, competition experiments confirmed that imipenem had common binding sites with basic amino acids in the OprD channel, but not with gluconate or glucose.

Identification and characterization of hematopoietic stem cells from the yolk sac of the early mouse embryo

The yolk sac is the first site of hematopoiesis in the mammalian embryo. However, little is known about the initial stem cells in the yolk sac. We have isolated hematopoietic stem cells from early mouse embryonic yolk sac by using a sequential protocol of nonadherence to plastic, density gradient centrifugation, immunocytoadherence, and cell sorting. Isolated, nonadherent, density < 1.077-g/cm3, surface antigen AA4.1+, wheat germ agglutinin bright (WGAbright) cells give rise to multiple lineages, including T cells, B cells, and myeloid cells, as detected by using fetal thymus organ culture, S17 stromal feeder layers, or methylcellulose culture colony-forming cells, respectively. AA4.1+, WGAbright cells expressed high levels of heat-stable antigen (HSA) and CD45 (Ly-5) but did not significantly express major histocompatibility complex antigens, CD44, or Sca-1. Peak stem cell concentration is reached by day 11, before stem cells can be found in the liver, omentum, or thymus. In vivo long-term reconstitution of lethally irradiated mice was effected by as few as 720 AA4.1+, WGAbright yolk sac cells, but it required addition of a subset of bone marrow cells capable of providing immediate (short-term) radiation protection. Yolk sac donor-derived T cells, B cells, and macrophages were readily identified 6 months after transfer of yolk sac-derived stem cells. We suggest that, because of their cell surface phenotype as well as their capacity to differentiate in vitro and in vivo, the cells isolated from the mouse embryonic yolk sac may include the most primitive hematopoietic pluripotential stem cells yet identified.

Fluorine-18 and carbon-11 labeled amphetamine analogs--synthesis, distribution, binding characteristics in mice and rats and a PET study in monkey

No-carrier-added (NCA) (+-)-p-[18F]fluoroamphetamine (2a) and (+-)-6-[18F]fluoro-3,4-methylene-dioxy-amphetamine (2b) were synthesized through a multistep synthesis by nucleophilic substitution of the appropriate precursors (p-nitrobenzaldehyde, 1a and 6-nitropiperonal 1b, respectively) with [18F]fluoride followed by condensation with nitroethane and reduction with LAH in 20-30% yield (EOB) in a synthesis time of 90-109 min from EOB. NCA (-)-[11C]methamphetamine (4a) and (+-)-3,4-methylene-dioxy-N-[11C]methamphetamine (4b) were synthesized by methylation of the appropriate desmethyl precursors 3a and 3b with [11C]H3I in 40-60% yield (EOB) in a synthesis time of 30 min from EOB. Animal studies in mouse and rat revealed that the relative tissue uptake of these radiotracers was kidneys > lungs > liver > spleen > brain > heart > blood. The uptakes of these radiotracers in mouse brain were high and similar at 5 min post-injection (approx. 5%/g) but radioactivity then declined rapidly (approx. 1%/g at 60 min post-injection). For compounds 2a and 2b, the activity in the femur did not increase with time indicating in vivo defluorination may not be the major route of metabolism. Monoamine uptake inhibitors (nomifensine, fluoxetine and nisoxetine) did not inhibit but enhance the uptake of (-)-[11C]methamphetamine (4a) in the rat brain by greater than 50%. A PET study in a Rhesus monkey revealed that the uptakes of (-)-[11C]methamphetamine in different brain regions were similar and the retention of the radioactivity in these regions remained constant throughout the study. Analysis of arterial plasma by HPLC showed that 50% of radioactivity remained as 4a at 60 min post-injection.

Immunolocalization of the G protein alpha subunit encoded by the GPA1 gene in Arabidopsis

Heterotrimeric GTP binding proteins (G proteins) are important signal transducers in lower eukaryotes and in animal cells. In plants, the occurrence of GTP binding proteins has been reported, but their biological function remains unclear. Two genes coding for G protein alpha subunits have been cloned: GPA1 in Arabidopsis and TGA1 in tomato. To gain some insights into the function of GPA1, we describe an extensive immunolocalization of GPalpha1, the gene product of GPA1, during Arabidopsis development. Our results show that the GPalpha1 is present through all stages of development and in all organs examined, with the exception of mature seeds. It is expressed in roots, floral stem, rosette leaves, cauline leaves, flowers, and seed pods. Interestingly, the level of GPalpha1 protein is higher in immature organs than in mature organs. GPalpha1 is present at a high level in the root meristem and elongation zone, in the shoot and floral meristems, and in the leaf primordium and floral organ (sepal, petal, stamen, and gynoecium) primordia. During flower development, dividing microspores, but not mature pollen, show high levels of GPalpha1. During pollination, GPalpha1 is present in the growing pollen tubes. The protein is also present in nectaries and developing ovules and, after fertilization, in developing embryos. In mature tissue, GPalpha1 is preferentially found in the vascular system but is also present in other cell types. The complexity of the GPalpha1 localization pattern suggests that GPalpha1 might be involved in different signaling pathways depending on the developmental stage.

Evidence that myocardial pertussis toxin substrates are uniquely altered in acute murine Chagas' disease in a manner unrelated to myocardial dysfunction

In an effort to correlate biochemical characteristics of the beta-adrenergic receptor complex with myocardial function, mouse myocardial GTP-binding proteins, specifically substrates for pertussis toxin (PT), were analysed with regard to the influence of infection with Trypanosoma cruzi, the causative agent of Chagas' cardiomyopathy. Infection was found to decrease in a non-uniform manner the magnitude of ADP-ribosylation in the PT substrates. High detergent concentrations attenuated the infection-associated decrease in PT-dependent ADP-ribosylation. Infection also altered the kinetics of the PT-dependent ADP-ribosylation reaction from a time course wherein maximal PT-dependent ADP-ribosylation occurred after 12 h incubation in control animals to one in which maximal PT-dependent ADP-ribosylation occurred after 3 h incubation and thereafter declined. Immunochemical analysis of the PT-substrates revealed an infection-associated decrease in alpha i1, alpha o, an increase in alpha i2 and no change in alpha i3. Verapamil treatment, which prevents the clinical consequences of infection, did not influence any of the infection-associated changes in PT-dependent ADP-ribosylation of GTP-binding protein substrates or their immunochemical properties. Complementary studies using isolated rat neonatal cardiocytes infected with the parasite further substantiated the finding that the infection-associated decrease in PT-dependent ADP-ribosylation and the associated change in the kinetics of the reaction were properties uniquely associated with the presence of the parasite.

DNA excision repair as a component of adaptation to low doses of ionizing radiation in Escherichia coli

In this study we examined whether or not DNA excision repair is a component of adaptation induced by very low-dose ionizing radiation in Escherichia coli, a well-characterized prokaryote, and investigated the relationship between enhanced excision repair and the SOS response. Competent E. coli cells were irradiated using low doses (0.1-10 Gy) of 137Cs gamma-rays, allowed to recover for 2 h and were then transformed using pUC18 DNA containing approximately 22 oxidized thymine residues (thymine glycols) per molecule. Successful transformants were identified by recovery of plasmid-borne ampicillin resistance and the resulting data (colony counts) were used to calculate ratios of plasmid recovery in irradiated to control cells. Results showed that cells irradiated with very low doses (0.1-0.5 Gy) were up to 30-40% more efficient at utilizing thymine glycol-containing pUC18 DNA. The enhanced excision repair by very low doses (< 0.5 Gy) of gamma-rays was shown to be independent of the recA-controlled SOS response in experiments using recA cells or cells carrying recA-lacZ gene fusions. The stimulating effect in AB1157 prototype cells were subsequently confirmed using a DNA precipitation assay in which DNA incision events were accumulated by inhibiting DNA ligation with ethidium bromide. Our data suggest that there seems to be narrow 'windows' of dose-effect for the induction of SOS-independent DNA excision repair. Being similar to mammalian cell studies, the dose range for this effect was about 200-fold less than D37 for radiation survival.

Efficient inhibition of human leukocyte elastase and cathepsin G by saccharin derivatives

A series of saccharin derivatives I has been synthesized and evaluated for their inhibitory activity toward human leukocyte elastase and cathepsin G. Most of the compounds were found to be efficient and time-dependent inhibitors of elastase. Inactivated elastase was found to regain its activity almost fully after 24 h (80-90% activity) and the half-lives of reactivation ranged between 12-15 h. Addition of hydroxylamine to fully-inactivated enzyme led to rapid and complete recovery of enzymatic activity. A tentative mechanism of action is proposed on the basis of biochemical and model studies.

Modulation of allosteric interactions in neurophysin induced by succinylation of serine-56 or cleavage of residues 1-8

Neurophysin is an allosteric protein in which peptide binding and self-association are positively linked. Reaction of neurophysin with succinic anhydride led to a large decrease in peptide affinity assignable to succinylation of a serine or threonine hydroxyl group. To identify the residue involved, acetimidated protein was reacted with [14C]succinic anhydride and the active and inactive components were separated by affinity chromatography. Performic acid oxidation and tryptic and Asp-N mapping of the two components, followed by automated Edman degradation, allowed identification of the critical residue as Ser-56. This residue is not a direct participant in peptide binding and is distant from the subunit interface of the dimer, but it is immediately adjacent to the site of one of the known mutations associated with familial diabetes insipidus. Examination in solution of the peptide affinity of neurophysin succinylated at Ser-56 indicated a binding affinity approximately 1/20th that of the native protein or of protein succinylated at other residues, and a loss of the normal dependence of binding affinity on protein concentration. Under the same buffer conditions, loss of the concentration dependence of binding, in addition to the previously demonstrated loss of binding affinity, also accompanied excision of residues 1-8, an effect attributed to the loss of binding site residue Arg-8. However, in contrast to the effects of succinylation on native neurophysin, only minor effects of succinylation on the binding affinity of the des-1-8 protein were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of the binding sequences for the product of the Arabidopsis floral homeotic gene AGAMOUS

The Arabidopsis floral homeotic gene AGAMOUS (AG) is required for normal flower development. The deduced AG protein contains a region which shares substantial sequence similarity with the DNA-binding domains of known transcription factors, SRF (human) and MCM1 (yeast). Therefore, it is likely that AG is also a DNA-binding protein regulating transcription of floral genes. We describe here several experiments to characterize AG-DNA binding in vitro. We show that AG indeed binds a DNA sequence matching the consensus of SRF targets. Further, we have selected the AG-binding sequences from a pool of random oligonucleotides, and deduced an AG-binding consensus sequence of TT(A/T)CC(A/T)(A/t)2(T/A)NNGG(-G)(A/t)2. We have demonstrated that AG binds to the consensus region of three of the oligonucleotides by footprinting analysis. Finally, we have examined AG's relative binding affinity for different sequences, as compared to SRF, by gel mobility shift analysis. Our results indicate that AG is a sequence-specific DNA-binding protein, and that the AG-binding consensus sequence is similar to those of MCM1 and SRF.

Mechanism-based inhibitors of serine proteinases based on the Gabriel-Colman rearrangement

Neutrophil-derived mediators such as, for example, the serine proteinase elastase, cathepsin G and proteinase 3, play a critical role in inflammatory lung disease. This report describes the design, synthesis and in vitro inhibitory activity of some novel mechanism-based inhibitors of human leukocyte elastase and cathepsin G. The design of the inhibitors is based on the Gabriel-Colman rearrangement. The behavior of the synthesized compounds toward elastase and cathepsin G with respect to inhibitory prowess, mode of interaction, specificity, etc., has been found to be dependent on the recognition and reactivity elements present in each inhibitor.